Presentation on theme: "Flavoring agents. Flavor has a profound influence on the consumption of food three types of flavoring additives: o flavorings o flavor enhancers o (non-nutritive)"— Presentation transcript:
Flavor has a profound influence on the consumption of food three types of flavoring additives: o flavorings o flavor enhancers o (non-nutritive) sweeteners More than 1500 substances are used as food flavorings. The majority are of natural origin or are nature-identical
Only a few synthetic substances have been approved as food flavoring. Examples are ethylvanillin, ethylmaltol, and anisylacetone
The most widely used flavor enhancer is salt (sodium chloride, NaCl). It is also a preservative and a nutrient. Generally, it is primarily regarded as a food additive. A well-known toxic effect of NaCl is high blood pressure.
Flavor enhancers intensify or modify the flavor of food. They have no taste of their own. such as monosodium glutamate (MSG) and various nucleotides. These substances are present in Japanese seaweed (Laminaria japonica, traditionally used for seasoning), mushrooms, tomatoes, peas, meat, and cheese.
They are often used in soups, sauces and oriental food. No known adverse effects of flavor enhancers have been reported, except for the case of MSG.
MSG It is also a synthetic product. MSG is an excitatory neurotransmitter. It has been shown to cause permanent lesions of the hypothalamus in newborn rats and mice. Presumably, this is attributable to immaturity of the blood-brain barrier. Further, in young mice and rats, lesions of the retina have been reported after large doses of glutamate.
Humans have also been found to be sensitive to food to which MSG has been added as a flavor enhancer. The symptoms, known as “Chinese restaurant syndrome,” include loss of feeling, general weakness, and heart palpitations. Humans have been described to be sensitive to food to which MSG had been added. The symptoms include numbness, general weakness, and heart palpitations
Sweeteners Sweeteners present the consumer with one of the most important taste sensations. For nutritional and health reasons, however, there is a growing need for sugar substitutes in food that are non-nutritive, i.e., noncaloric, and noncariogenic. Two important noncaloric synthetic sweeteners are saccharin and aspartame.
SACCHARIN In 1912 it was prohibited in the US on the basis of acute toxicity tests. Up to now, no mutagenicity has been found. However, long-term animal tests showed a higher incidence of bladder cancer. Although it is difficult to extrapolate from experimental animals to the human situation, the present average level involves risks of cancer. Therefore, the use of saccharin in food is still approved in the US and in Europe.
ASPARTAME Aspartame was discovered in the early 1960s Aspartame is a dipeptide, consisting of the amino acids phenylalanine and aspartic acid. It is digested and absorbed by the body It is 200 times sweeter than saccharose and is an excellent sweetener for dry products. At high temperature and low pH, aspartame is gradually hydrolyzed, losing its sweetness.
It is suitable as table top sweetener, in chewing gum, in soft drinks, dairy products, ice cream, and dessert mixes. Results from toxicity tests suggest that aspartame has no adverse effects on humans even when extreme amounts of 8 mg/kg body weight are taken in. The ADI for aspartame is 40 mg/kg body weight.
Preservatives Preservatives keep food edible for long periods of time by preventing the growth of microorganisms such as bacteria and fungi. Although the public perceives preservatives in particular as hazardous, they are not only harmless at the levels ingested but in fact beneficial in that they reduce or prevent the risks due to bacterial and fungal contamination
Antimicrobial Common antimicrobial food additives are benzoic acid and benzoates, sorbic acid and sorbates, short-chain organic acids (acetic acid, lactic acid, propionic acid, citric acid), parabens (alkyl esters of p-hydroxybenzoic acid), sulfite, and nitrite. Most of these substances are believed to be safe for application in food. They are easily excreted and metabolized by both animal and man. An exception should be made for one of them, namely nitrite. The intake of nitrite can lead to the formation of nitrosamines, which are well-known carcinogens.
Nitrates and nitrites are used to preserve meats. For example, they contribute to the prevention of growth of Clostridium botulinum, the bacterium that produces the well- known highly potent botulinum toxin. The adverse effects after intake of nitrates and nitrites are methemoglobinemia and carcinogenesis (from the formation of nitrosamines)
Nitrite Nitrite oxidizes (ferrous) hemoglobin to methemoglobin, which cannot bind oxygen. This may lead to a state of anoxia. The consumption of meat with high levels of nitrate and nitrite as well as of other dietary nitrate sources, such as drinking water and spinach, has resulted in life-threatening methemoglobinemia, especially in young children. Newborns are (transiently) deficient in NADH- reductase, the major system responsible for methemoglobin reduction.
Nitrite (either ingested directly or indirectly via the reduction of nitrate) also reacts with secondary amines under the formation of a variety of nitrosamines, e.g., dimethylni trosamine, diethylnitrosamine, and N- nitrosopyrrolidine.
Nitrosamine formation can take place in food and in vivo. The acidic conditions in the stomach favor nitrosamine formation. Nitrosamines are mutagens as well as carcinogens. They induce cancer in a variety of organs, including the liver, respiratory tract, kidney, urinary bladder, esophagus, stomach, lower gastrointestinal tract, and pancreas. Nitrosamines need biotransformation for their activation. The bioactivation of nitrosamines is mediated by cytochrome P-450. It involves oxidative N-dealkylation, followed by a sequence of rearrangements to yield the alkylating alkylcarbonium ions
It should be noted that a decrease in the incidence of botulism may be accompanied by an increase in the formation of carcinogenic nitrosamines, as a result of an increase in the nitrite level of the meat (products).
From a food toxicological point of view, three types of nitrosamines are of importance: dialkyl nitrosamines, acylalkylnitrosamines, and nitrosoguanidines. Cyclic nitrosamines are similar to the dialkyl type. The nitrogen atom becomes part of the heterocyclic ring. Nitrosoguanidines are a special class of highly reactive nitrosamides.
One of the most effective inhibitors of nitrosation is ascorbic acid. This vitamin reacts rapidly with nitrite to form nitric oxide and dehydroascorbic acid. In that way, it can inhibit the formation of dimethylnitrosamine by more than 90%. Other inhibitors of nitrosation are gallic acid, sodium sulfite, cysteine, and tannins.
Nitrosamine levels in food also depend on the temperature at which food is prepared. Cooking can increase the nitrosamine level in food. frying can increase the nitrosamine level in bacon quite considerably. Up to 135° C, cooking or frying does not result in detectable nitrosamine formation. Above 175°C, however, the nitrosamine levels increase rapidly.
Nitrite addition to fresh meat and food products is still under discussion because of the toxicological hazards. Up to now, banning of this additive has been blocked by the food industry. It is stressed that so far no other antimicrobial agent has been found that can provide protection against Clostridium botulinum as effectively as nitrite. In some EU countries (but not in Germany and the UK) and the US, nitrite addition to fresh meat is allowed up to a maximum of 200 ppm.
Antioxidants Antioxidants are used to protect oils, fats, and shortening against oxidative rancidity and to prevent the formation of toxic degradation products and polymers. Many foods may undergo oxidation, but particularly those containing fats are susceptible to changes in color, odor, taste, and nutritional value. Unsaturated fatty acids are readily peroxidized in the presence of molecular oxygen.
The peroxidation products may induce toxic effects. Also, in biological systems peroxidation of lipids may have severe adverse consequences. Peroxidation of polyunsaturated fatty acids is believed to be involved in disturbing the integrity of cellular membranes, the pathogenesis of hemolytic anemia, and pulmonary and hepatic injury. Secondary peroxidation products, e.g., hydroxynonenal, can form adducts with DNA.